Cool discharge tubes of hollow ring-like construction



Aug. 22, 1967 H. MENOWN ETAL COOL DISCHARGE TUBES OF HOLLOW RING-LIKECONSTRUCTION Filed April 15, 1964 J m F 644 fllmm m M w M BY ATTQRNEYUnited States Patent 3,337,764 COOL DISCHARGE TUBES OF HOLLOW RING-LIKECONSTRUCTION Hugh Menown and Ronald Ernest Lake, Essex, England,assignors to English Electric Valve Company, Limited, London, England, aBritish company Filed Apr. 15, 1964, Ser. No. 359,946 Claims priority,application Great Britain, Apr. 29, 1963, 16,697/ 63 10 Claims. (Cl.313-30) This invention relates to discharge tubes and has for its objectto provide improved, economical and mechanically strong discharge tubestructures suitable for high power operation and which will lendthemselves to eflicient forced cooling by fluid coolants which may begas or liquid. The principal, though not the exclusive application ofthe invention, is to high power thyratrons, e.g. high power hydrogenfilled thyratrons.

In various types of discharge tube and in particular in high powerthyratrons, very substantial amounts of heat are produced on one or moreof the electrodes. For example, in the case of a high power thyratron,very considerable amounts of heat are produced on the grids, especiallyon the so-called second grid and power limitation is often set by theability to cool this grid. In many tubes also, including high powerthyratrons, there are other electrodes the anode in particular--whichrequire cooling if high powers are to be produced from a tube which isrelatively small physically..A tube structure which will lend itself toefiicient forced cooling by fluid coolant therefore offers verysubstantial advantages and the present invention seeks to provideimproved tube structures which, from the point of view of cooling, are agood deal better than the normal structures at present generallyemployed and wherein the electrodes are housed in the customary more orless cylindrical envelope and forced cooling, it any, is effected byforcing the coolant past the outside of the envelope with improvedcooling obtained by such expedients as providing that portion of theanode which is outside the envelope with external fins or the like inthe coolant stream.

According to this invention in its broadest aspect the hermeticallysealed envelope of a hermetically sealed discharge tube comprises aninner substantially cylindrical composite wall having at least one partof its length made of metal and the remainder of its length made ofinsulating material, said wall constituting the wall of a coolantconduit passing axially through the tube, the remaining walls of theenvelope being outwardly of and extending around said inner wall toprovide a hermetically sealed envelope space encircling said conduit,the electrodes of the tube including at least one electrode of high heatloading and which is in good heat conducting relationship with saidmetal length.

Preferably said one electrode includes a portion which is of hollowring-like construction having its innermost wall constituted by saidmetal length.

In a preferred construction in accordance with the invention said oneelectrode includes an inner portion which is of hollow-ring-likeconstruction having its innermost wall constituted by said metal lengthand an outer portion also of hollow ring-like construction encirclingand spaced from said inner portion, said outer portion being supportedby an outer substantially cylindrical supporting wall structure co-axialwith the coolant conduit.

Preferably the insulating material is ceramic material though othersuitable insulating materials may be used.

Where necessary any of the electrodes may be made of or supported bydouble walled structures arranged for the passage of coolanttherethrough. In a construction in which said one electrode has innerand outer portions of 3,337,764 Patented Aug. 22, 1967 hollow ring-likeconstruction, the outer portion encirclmg and being spaced from theinner and the inner portion having its innermost wall constituted by theaforesaid metal length of the coolant conduit, said metal length may beprovided with apertures giving access for coolant to the interior ofsaid inner portion. In this case one or more coolant pipes hermeticallysealed to and bridging the space between the inner and outer portionsmay be provided to pass coolant from the interior of the inner portionto the interior of the outer portion, coolant which has passed throughsaid portions and said pipe or pipes being taken oif from the interiorof the outer portion.

As stated the principal, though not the exclusive application of theinvention is to thyratrons.

According to a feature of this invention a thyratron has a hermeticallysealed envelope comprising an inner substantially cylindrical compositewall having an intermediate part of its length made of metal, said innercomposite wall constituting a coolant conduit extending axially throughthe thyratron; an outer insulating sleeve coaxially surrounding aninsulating length forming one end of the conduit wall; a ring-like anodebetween said sleeve and said insulating length of conduit wall andsealed to both; a second grid structure comprising a hollow innerring-like portion having its innermost wall constituted by the metallength of the conduit wall and an encircling outer ring-like portionspaced from said inner portion, the inner portion being sealed to saidinsulating length of conduit wall and the outer portion being sealed tosaid sleeve, said inner and outer portions having end walls facing andspaced in the axial direction from a wall of the anode; a secondco-axial insulating sleeve of substantially the same diameter as thefirst and interposed between a radial wall of the outer portion of thesecond grid structure and sealed at one end thereto, said second sleevebeing sealed at its other end to one side of a substantially annularpriming electrode at right angles to the tube axis and having its innercircular end approximately opposite the space between the inner andouter portions of the second grid structure; a third co-axial insulatingsleeve of substantially the same diameter as the other two and sealed atone end to the other side of the priming electrode; a cathode shieldhaving a substantially coaxial cylindrical portion and sealed at one endto the remaining end of the third sleeve; cathode means in the annularspace between the cylindrical portion of the cathode shield and anotherinsulating length of the coolant conduit; and means completing thehermetically sealed envelope in which the cathode means and theoperating parts of the cathode shield and the priming, second grid andanode structures are situated. In the case of a hydrogen thyratron withindirectly heated cathode means, the hermetically sealed envelope mayalso include a space housing one or more hydrogen capsules adapted toreplenish the hydrogen filling, electrical heaters on said capsule orcapsules and connections between the cathode heating means and saidelectrical heater or heaters.

If desired there may be provided apertures in the innermost wall of theinner portion of said second grid, said apertures providingcommunication between the interior of the conduit and the interior ofsaid inner portion; pipes providing communication between the interiorsof the inner and outer portions of the second grid across the spacebetween said portions; and means providing egress for coolant from theinterior of said outer portion.

The coolant may be any suitable gas or liquid, e.g. air or transformeroil.

The invention is illustrated in the accompanying simplified drawingswhich show one embodiment of the invention as applied to a high powerhydrogen filled thyratron. In the drawings, FIGURE 1 is a simplifiedelevation view in centre line section of a high power hydrogen filledthyratron; FIGURE 2 is a plan view looking down on the tube of FIGURE 1;FIGURE 3 is a plan view taken in the same direction as FIGURE 1 but withthe anode removed and FIGURE 4 is a fragmentary section view of aportion of a thyratron of alternate construction.

Referring to the drawings, it will be seen that the general envelopearrangement is quite different from that of an ordinary known dischargetube inasmuch as it is constructed to provide an axial conduit 1 runningup the middle of the tube and with the various electrodes disposedaround it. This, conduit is composed, in effect, of lengths ofinsulatingpreferably ceramic-material and metal. The part of the conduitwhich is uppermost in FIGURE 1 is composed of a cylinder 2 of ceramicmaterial which is co-axially within and spaced from an external sleeve 3also of ceramic material. In the space between the parts 2 and 3 andround the upper end of the conduit is a ringlike channel-sectioned anode4 with the openside of the channel uppermost and the parallelcylindrical walls thereof sealed to the parts 2 and 3. Next below theanode 4 is a so-called second grid which consists of two separatestructures 5 and 6. The structure 5 is of hollow ringlike form with asmall step in the ring between a cylindrical wall 5a and a secondcylindrical wall 5b of rather smaller diameter, the second cylindricalwall 5b being of the same diameter as the part 2 and constituting ametallic length of the conduit wall. The outer wall of the structure 5is similarly stepped and includes two cylindrical portions 50 and 5d.

The second structure 6 includes outer and inner cylindrical walls 6a and6b of which the former is sealed to the sleeve 3 and the latter extendsbelow the former and continues into an annular wall 60 which leaves agap 6d providing access to the interior of the structure 6. Theuppermost walls 5e and 6e of the structures 5 and 6 are co-planar. Theyface and are spaced from the annular wall of the anode 4. The walls 50and 6b are spaced from one another and define a cylindrical gap forelectron flow in directions parallel to the axis.

The first or priming grid 7 of the thyratron is of annular form and ishollow being made of suitable metal bent back on itself in re-entrantfashion with the re-entrant bend projecting into the tube as shown. Oneof the two parallel walls of the grid 7 is sealed to one end of a shortceramic sleeve 8, the other end of which is sealed to the wall 6c. Theother of the parallel walls of the grid 7 is sealed to one end of afurther short ceramic sleeve 9. The ceramic parts 3, 7 and 9 are all ofthe same diameter.

The upper end of the wall 5b is sealed to the lower end of the part 2and the lower end of the said wall 512 is sealed to the upper end of aceramic cylinder 10 which also forms part of the wall of the conduit 1.Co-axially surrounding the part 10 is a hollow cathode shield 11 formedof metal bent as shown to provide an annular portion 11a and acylindrical portion 11b. The annular portion 11a is sealed to the lowerend of the sleeve 9.

In the space between the cylindrical portion 11b and the ceramic member10 is a cathode arrangement which may be a single cathode of ring formor, as shown, may consist of a number of similar cathode units disposedin a ring round the conduit. These cathode units are of the indirectlyheated type and of known construction being only schematicallyrepresented. The only parts of these cathode structures which arereferenced are the cathode heaters 12.

Below the ceramic member 19 is a ceramic cylinder 13 which again formspart of the central conduit wall and which is surrounded by a ceramicsleeve 14 which is of the same diameter as the cylindrical portion 11bof the cathode shield and is sealed to the lower end thereof. In thespace between the parts 13 and 14 are mounted hydrogen reservoirs ofknown form, e.g. hydrogen filled palladium tubes with heaters 15 woundon them. The heaters of the hydrogen reservoirs are shown in the exampleillustrated as being in parallel with the cathode heaters, though thisarrangement is not necessary and separate connections may be provided ifrequired. The heater connections shown are referenced 16 and suitableconnections (not shown) are provided for the cathode or cathodes. At thebottom the parts 13 and 14 are sealed to a metal closure ring 17.

With this construction, and assuming that the wall 512 is a solidunperforated wall (as it could be) the hermetically sealed envelope ofthe tube will consist of the portion of the conduit wall between thering 17 and the annular face of the anode 4, the said annular face, thepart of the member 3 between the annular face of the anode and the wall6e, the said wall 6e, the walls 6b and 6c, the sleeve 8, the grid 7, thesleeve 9, the cathode shield 11, the sleeve 14 and the closure wall 17.Very good cooling can be obtained by pumping air, transformer oil orother suitable coolant up the central conduit, for the second grid hasits wall 50, where much heat may be generated, in excellent heatconducting relationship with the wall 5b which itself forms part of theconduit. Also the cooling of the anode 4 is inherently very good.Furthermore, the hollow construction of the priming grid and the cathodeshield considerably facilitates cooling of these electrodes also,though, of course, it is not necessary to make them of hollowconstruction.

If desired, any or all of the electrodes which are of hollowconstruction-and in the illustrated embodiment this includes the priminggrid and the cathode shield may be force cooled by pumping coolantthrough the electrode or electrodes in question using their hollowconstruction to provide coolant paths through them. Also the wall 5b maybe provided with apertures 19 so that coolant from the conduit can enterthe structure 5. If this is done this wall will no longer constitutepart of the hermetically sealed envelope but its place as part of theenvelope will be taken by the remaining walls of'the structure 5. Ifcoolant access apertures are provided in the wall 5b it is preferred toprovide coolant paths from the interior of the structure 5 to theinterior of the structure 6 so that coolant paths will exist between theconduit 1 and the gap 6d as illustrated in FIGURE 4. Such coolant pathsmay be provided by short pipes between the interiors of the structures 5and 6 bridging the gap between the walls 50 and 6b. Three such pipes,referenced 18, appear in the View of FIGURES 3 and 4. By suitablyangularly spacing the pipes around the axis, a sufiicient coolant flowcan be obtained without appreciable interference with the electron flowup between the walls 5c and 6b.

The invention is not limited to the particular construction shown,though this is considered to be a good one. For example, the hydrogenreservoirs in the illustrated embodiment are shown in the annular spacebelow the cathode, but obviously the hydrogen reservoirs need not belocated in this position.

We claim:

1. A discharge tube having a hermetically sealed envelope whichcomprises an inner substantially cylindrical composite wall having atleast one part of its length made of metal and a remaining part of itslength made of insulat-ing material, said wall constituting the wall ofa substantially cylindrical coolant conduit passing axially through thetube, the remaining walls of the envelope being outwardly of andextending around said inner wall to provide a hermetically sealedenvelope space encircling said conduit, the electrodes of the tubeincluding at least one electrode of high heat loading and which is ingood heat conducting relationship with said metal length, said oneelectrode including an inner portion which is of hollow ring-likeconstruction substantially enclosing an an ular cavity therein andhaving its innermost wall constituted by said metal length.

2. A tube as claimed in claim 1 wherein said one elecm) trode includesan outer portion also of hollow ring-like construction encircling andspaced from said inner portion, said outer portion being supported by anouter substantially cylindrical supporting wall structure coaxial withthe coolant conduit.

3. A tube as claimed in claim 1 wherein the insulating material isceramic material.

4. A tube as claimed in claim 1 wherein said one electrode includes anouter portion of hollow ring-like construction, the outer portionencircling and being spaced from the inner and said metal length beingprovided with apertures giving access for coolant to the interior ofsaid inner portion.

5. A tube as claimed in claim 5 wherein one or more coolant pipeshermetically sealed to and bridging the space between the inner andouter portions are provided to pass coolant from the interior of theinner portion to the interior of the outer portion, coolant which haspassed through said portions and said pipe or pipes being taken off fromthe interior of the outer portion.

6. A thyration having a hermetically sealed envelope com-prising aninner substantially cylindrical composite wall having an intermediatepart of its length made of metal, said inner composite wall constitutinga coolant conduit extending axially through the thyration; an outerinsulating sleeve co-axially surrounding an insulating length formingone end of the conduit wall; a ring-like anode between said sleeve andsaid insulating length of conduit wall and sealed to both; a second gridstructure comprising a hollow inner ring-like portion having itsinnermost wall constituted by the metal length of the conduit wall andan encircling outer ring-like portion spaced from said inner portion,the inner portion being sealed to said insulating length of conduit walland the outer portion being sealed to said sleeve, said inner and outerportions having end walls facing and spaced in the axial direction froma wall of the anode; a second coaxial insulating sleeve of substantiallythe same diameter as the first and interposed between a radial wall ofthe outer portion of the second grid structure and sealed at one endthereto; a substantially annular priming electrode at right angles tothe tube axis and having its inner circular end approximately oppositethe space between the inner and outer portions of the second gridstructure; said second sleeve being sealed at its other end to one sideof the priming electrode; a third co-axial insulating sleeve ofsubstantially the same diameter as the other two and sealed at one endto the other side of the priming electrode; a cathode shield having asubstantially co-axial cylindrical portion and sealed at one end to theremaining end of the third sleeve; cathode means in the annular spacebetween the cylindrical portion of the cathode shield another insulatinglength of the coolant conduit; and means completing the hermeticallysealed envelope in which the cathode means and the operating parts ofthe cathode shield and the priming, second grid and anode structures aresituated.

7. A thyratron as claimed in claim 6 wherein the hermetically sealedenvelope also includes a space housing at least one hydrogen capsuleadapted to replenish the hydrogen filling, electrical heaters on said atleast one capsule and connections between the cathode heating means andsaid electrical heater or heaters.

8. A thyratron as claimed in claim 7 wherein there are providedapertures in the innermost wall of the inner portion of said secondgrid, said apertures providing communication between the interior of theconduit and the interior of said inner portion; pipes providingcommunications between the interiors of the inner and outer portions ofthe second grid across the space between said portions; and meansproviding egress for coolant from the interior of said outer portion.

9. A tube as claimed in claim 1 having a coolant gas within saidconduit.

10. A tube as claimed in claim 1 having a coolant liquid within saidconduit.

References Cited UNITED STATES PATENTS 2,609,517 9/1952 McCullough 3l3.23O 2,654,844 10/1953 Eitel et al 313-249 FOREIGN PATENTS 844,1558/1960 Great Britain.

DAVID J. GALVIN, Primary Examiner.

1. A DISCHARGE TUBE HAVING A HERMETICALLY SEALED ENVELOPE WHICHCOMPRISES AN INNER SUBSTANTIALLY CYLINDRICAL COMPOSITE WALL HAVING ATLEAST ONE PART OF ITS LENGTH MADE OF METAL AND A REMAINING PART OF ITSLENGTH MADE OF INSULATING MATERIAL, SAID WALL CONSTITUTING THE WALL OF ASUBSTANTIALLY CYLINDRICAL COOLANT CONDUIT PASSING AXIALLY THROUGH THETUBE, THE REMAINING WALLS OF THE ENVELOPE BEING OUTWARDLY OF ANDEXTENDING AROUND SAID INNER WALL TO PROVIDE A HERMETICALLY SEALEDENVELOPE SPACED ENCIRCLING SAID CONDUIT, THE ELECTRODES OF THE TUBEINCLUDING AT LEAST ONE ELECTRODE OF HIGH HEAT LOADING AND WHICH IS INGOOD HEAT CONDUCTING RELATIONSHIP WITH SAID METAL LENGTH, SAID ONEELECTRODE INCLUDING AN INNER PORTION WHICH IS HOLLOW RING-LIKECONSTRUCTION SUBSTANTIALLY ENCLOSING AN ANULAR CAVITY THEREIN AND HAVINGITS INNERMOST WALL CONSTITUTED BY SAID METAL LENGTH.